This invention relates generally to human/computer interface devices, and more particularly to computer input devices such as mice, trackballs, etc.
Virtual reality computer systems provide users with the illusion that they are part of a "virtual" environment. A virtual reality system will typically include a personal computer or workstation, specialized virtual reality software, and virtual reality I/O devices such as head mounted displays, pointer gloves, 3D pointers, etc.
For example, a virtual reality computer system can allow a doctor-trainee or other human operator or user to "manipulate" a scalpel or probe within a computer-simulated "body", and thereby perform medical procedures on a virtual patient. In this instance, the I/O device is typically a 3D pointer, stylus, or the like. As the "scalpel" or "probe" moves within the body image displayed on the screen of the computer system, results of such movement are updated and displayed so that the operator can gain the experience of such a procedure without practicing on an actual human being or a cadaver.
For virtual reality systems to provide a realistic (and therefore effective) experience for the user, sensory feedback and manual interaction should be as natural as possible. As virtual reality systems become more powerful and as the number of potential applications increases, there is a growing need for specific human/computer interface devices which allow users to interface with computer simulations with tools that realistically emulate the activities being represented within the virtual simulation. Such procedures as laparoscopic surgery, catheter insertion, and epidural analgesia should be realistically simulated with suitable human/computer interface devices if the doctor is to be properly trained.
While the state of the art in virtual simulation and medical imaging provides a rich and realistic visual feedback, there is a great need for new human/computer interface tools which allow users to perform natural manual interactions with the computer simulation. For medical simulation, there is a strong need to provide doctors with a realistic mechanism for performing the manual activities associated with medical procedures while allowing a computer to accurately keep track of their actions.
There are number of devices that are commercially available for interfacing a human with a computer for virtual reality simulations. There are, for example, such 2-dimensional input devices such as mice, trackballs, and digitizing tablets. However, 2-dimensional input devices tend to be awkward and inadequate to the task of interfacing with 3-dimensional virtual reality simulations. In contrast, a 3-dimensional human/computer interface tool sold under the trademark Immersion PROBE.TM. is marketed by Immersion Human Interface Corporation of Palo Alto, Calif., and allows manual control in 3-dimensional virtual reality computer environments. A pen-like stylus allows for dexterous 3-dimensional manipulation, and the position and orientation of the stylus is communicated to a host computer. The Immersion PROBE has six degrees of freedom which convey spatial coordinates (x, y, z) and orientation (role, pitch, yaw) of the stylus to the host computer.
While the Immersion PROBE is an excellent 3-dimensional interface tool, it may be inappropriate for certain virtual reality simulation applications. For example, in some of the aforementioned medical simulations three or four degrees of freedom of a 3-dimensional human/computer interface tool is sufficient and, often, more desirable than five or six degrees of freedom because it more accurately mimics the real-life constraints of the actual medical procedure. Therefore, a less complex, more compact, lighter weight, lower inertia and less expensive alternative to six degree of freedom human/computer interface tool is desirable for certain applications.